[0001] The present invention relates to heating of long subsea flowlines conducting hydrocarbons
and long distance power supply via subsea cables. In particular it relates to the
method known in the art as direct electric heating, wherein electric power is used
to heat the pipelines in order to prevent hydrate formation. The assembly is particularly
suitable for hydrate/wax prevention in long step-out flowlines by direct electric
heating of e.g. 25.4 cm to 76.2 cm (30") pipelines in the range of e.g. 60-300 km
or more.
Background
[0002] Direct electric heating (DEH) of long flowlines and large export pipelines provides
many advantages compared to alternative methods. DEH has been applied actively in
the past 10 years to prevent hydrate formation and is now breaking new ground that
was not previously being considered feasible. By using qualified technology and existing
design models, longer and larger pipelines can be heated intermittently or continuously.
[0003] Direct Electrical Heated Pipe in Pipe (DEHPIP) is a slightly different technological
approach to the same problem that have quite similar demands for the electrical power
supply system to drive them, hence most of the electrical energy supply system topologies
can be used to power both DEH and DEHPIP systems independent of end-fed or midpoint
fed topologies. Common for both systems is that the electric current flows axially
through the pipe wall causing direct heating of the pipeline.
Wet-insulated: Open Loop System
End-Fed Pipe
Center-Fed Pipe
Dry-insulated: Closed Loop System
End-Fed Pipe-in-Pipe
Center-Fed Pipe-in-Pipe
[0004] DEHPIP systems are sometimes described as Electrical Flowline Heating (EFH) systems
since EFH systems traditionally have been associated with the Dry Insulated (Pipe-in-Pipe)
flowline heating system technology, but the term can also be used as a general reference
to any flowline heating using electricity.
[0005] Electric Heating of Pipelines is attractive for short and long step outs as DEH operating
costs are considerably reduced compared to the use of chemicals. The technology is
unique and commercially and technically attractive. It allows for the use of DEH for
both infield flowlines, tie-backs and export pipelines with diameters around 15,4
cm (6") to 76,2 cm (30") and above. An increased number of DEH assemblies has been
evaluated for oil and gas fields or project developments concepts around the world
and the extension of this new technology will generally give higher flexibility in
operation of the fields during planned or unplanned shut downs. Material aging and
other failure mechanisms caused by high temperatures and water pressure are also of
great importance. Accuracy in design and analysis as well as industry experience are
important in solving project specific hydrate or wax issues in long DEH systems.
[0006] Using DEH can involve arranging a DEH cable along a steel pipeline. Current is guided
through the DEH cable in one direction and returned through the pipeline steel in
the return direction. Heat is generated in the pipeline steel, partly due to ohmic
resistance in the steel and partly due to induced heat, as the current is an alternating
current. As the contact between the DEH cable and the pipeline steel is not insulated
from the surrounding sea water, a fraction of the current will also flow through the
sea water and not in the pipeline.
[0007] Patent application publication
EP2166637 (Siemens Aktiengesellschaft) describes a power supply arrangement for direct electrical
heating (DEH) of a pipeline system. The power supply arrangement has a three phase
transformer and a compensation unit including a capacitor means, and is adapted to
feed electrical power to a single phase load.
[0008] WO2007011230 (Aker Kværner Engineering & Technology) describes a system for power supply to a
flowline heating circuit. An electric distribution cable (3) is connected to the system,
which extends to the subsea located pipeline (4) which is to be heated. In a subsea
location there are arranged 3-to-2 phase transformers which connect electric power
from a supply cable to sections of "piggyback" cables strapped onto the heated pipeline.
[0009] WO2006075913 describes a system for power supply to subsea installations, comprising electric
power supply cables for DEH of a pipeline. The system is configurable to provide 3-phase
power supply to an electric motor arranged subsea, when not heating the pipeline.
The invention
[0011] According to the invention there is provided a subsea direct electrical heating assembly
adapted to heat a hydrocarbon conducting steel (typically pipe-walls with ferromagnetic
or similar material properties) pipeline arranged subsea. The assembly comprises a
direct electrical heating cable (DEH cable) extending along and being connected to
the steel pipeline and a power transmission cable adapted to receive electric power
from a power supply, arranged onshore or at surface offshore, and to feed the direct
electrical heating cable. According to the invention the subsea direct electrical
heating assembly further comprises a power conditioning arrangement arranged at a
subsea location, in a position between the power transmission cable and the direct
electrical heating cable, wherein the power transmission cable extends from the offshore
or onshore power supply and down to the power conditioning arrangement.
[0012] The power transmission cable should be understood to mean any cable or plurality
of cables that transport electric power from an offshore topside or onshore location
to the subsea location of the power conditioning arrangement. It should be understood
that the power transmission cable also could receive electric power via another subsea
unit, such as a power distribution unit arranged subsea.
[0013] The power conditioning arrangement can advantageously comprise a subsea capacitor
arrangement. Since the DEH cable combined with the pipeline that shall be heated constitute
an inductive load, the use of a capacitor arrangement will adapt delivered power to
fit the load. That is, the power factor will be adjusted to balance the inductive
load with the power supply. As a result, the cross section of the power transmission
cable can be reduced compared to prior art solutions, in which power conditioning
was performed onshore or on a floating installation, far away from the load.
[0014] The power conditioning arrangement can also comprise a transformer. The power conditioning
arrangement can also comprise a reactor.
[0015] The direct electrical heating cable is preferably arranged along and attached to
the pipeline. A person skilled in the art knows this method as the piggyback solution.
[0016] A piggyback solution can also be used for a subsea power cable independent of DEH
or EFH. I.e. a power cable can, during pipe laying or before trenching, be strapped
to a hydrocarbon or produced-water or injection-water transfer pipeline, to establish
an electrical interconnection between two offshore installations or between onshore
and offshore installations. For long interconnections of this type or similar ones
without DEH a subsea reactor is suitable to overcome some of reactive power flow challenges
associated with critical cable lengths and transmission losses for high voltage ac-power
cables.
[0017] In an embodiment according to the present invention, the subsea direct electric heating
assembly is adapted to heat a plurality of pipeline sections which each constitutes
a part of a longer pipeline. In this embodiment the assembly comprises a plurality
of DEH cables arranged along and/or in proximity to the pipeline sections. For each
pipeline section a said power conditioning arrangement is arranged between the power
transmission cable and the section heating cables associated to each pipeline section.
[0018] In one embodiment, power from the power transmission cable is fed to a direct electrical
heating cable adapted to heat a pipeline extending between a subsea well and a subsea
compression facility, through the subsea power conditioning arrangement.
[0019] The subsea capacitor arrangement can be in the kV and kVAr range or above. Preferably
the capacitor arrangement comprises a capacitor element arranged within a tank that
prevents sea water entering the tank and getting into contact with the capacitor arrangement.
The tank is preferably pressure balanced and filled with a pressure compensation fluid.
[0020] On or off load tap-changer or tuning arrangements can be arranged in combination
with a magnetic gear in order to enable operation without penetration of a metallic
water barrier of the subsea capacitor unit's tank or housing.
[0021] Also, the transformer is preferably arranged within the same tank.
[0022] The on or off load tap-changer or tuning arrangements can be adjusted by ROV operations
or an electric or a hydraulic actuator as typically used for subsea valve operations.
[0023] The capacitor arrangement is preferably a variable capacitor arrangement. The capacitance
can then be adjustable between an upper and lower value, preferably by means of an
actuator arranged within the tank. In this embodiment the operator is able to condition
the delivered power to the load after installing the power conditioning arrangement,
i.e. tuning of the DEH loops or enhanced power level control.
[0024] Correspondingly, the transformer can be an adjustable transformer for tuning of DEH
loops or enhanced power level control.
[0025] One embodiment of an adjustable transformer is a transformer equipped with an on
or off load tap-changer arrangement preferably capable of a +/- 30% voltage control
range or more.
[0026] A second embodiment of an adjustable transformer is a transformer equipped with an
on load magnetic-field control arrangement preferably capable of a +/-30% voltage
control range or more, i.e. an adjustable air-gap or a Controllable Inductance Transformer.
[0027] Optionally one or more of the transformer out-put terminals can be equipped with
series reactors that can be tapped or short circuited in order to step the output
current.
[0028] Alternatively to adjustable transformers, solutions with semiconductor based power
electronics can be used to limit the voltage applied on a section with DEH or EFH,
i.e. typically thyristors in anti-parallel, transistors or other arrangements that
can be operated in similar manners as a soft-starter for continuous operation. The
semiconductors can be pressurized or located in a one atmosphere pressure controlled
chamber associated with or within the pressure compensated transformer tank/housing
or the tank of the power conditioning arrangement.
[0029] The above methods for tuning of DEH loops or enhanced EFH power level control can
generally be applied for power conditioning embodiments with single phase transformers,
3-to-2-phase transformers (typically Scott or Le Blanc connected) or 3-to-4-phase
transformers, but some will be better suited than others for specific solutions.
[0030] In an advantageous embodiment the power transmission cable comprises three phases
and three section heating cables are each connected between two different pairs of
phases of the power transmission cable. In one variation of this embodiment, the assembly
comprises three sets of section heating cables, wherein each set comprises two or
more section cables. A section heating cable is a DEH cable adapted to heat a pipeline
section. This will be described below with reference to the drawings.
[0031] Parallel pipelines or U-shaped return-pig-able flow lines or infield lines could
have parallel pipe sections with DEH applied separately with dedicated piggyback cables
on each parallel pipe section powered via a three-to-two phase transformers or three-to-four
phase transformers.
[0032] In an end-fed embodiment the power conditioning arrangement can be connected between
the power transmission cable and an end-fed pipeline section. One transformer phase
exits the tank through penetrator(s) and is connected to respective remote-end of
said pipeline section. Furthermore, a second transformer terminal is connected to
a section near-end connection cable that connects to a near-end on the pipeline section
between said respective ends. The section near-end connection cable is short-circuited
to a steel structure of the power conditioning arrangement as is also the second transformer
terminal. The steel structure can for instance be the tank structure.
[0033] In a midpoint embodiment the power conditioning arrangement can be connected between
the power transmission cable and a midpoint fed pipeline section. Two transformer
phases exit the tank through penetrators and are connected to respective ends of said
pipeline section. Furthermore, a third transformer terminal is connected to a section
midpoint connection cable that connects to a midpoint on the pipeline section between
said respective ends. The section midpoint connection cable is short-circuited to
a steel structure of the power conditioning arrangement as is also the third transformer
terminal. The steel structure can for instance be the tank structure.
[0034] In one particular embodiment the power conditioning arrangement is connected to a
plurality of DEH cables which are arranged along different pipelines.
[0035] In another but somewhat similar embodiment the power conditioning arrangement is
connected to a plurality of sets of a plurality of DEH cables, wherein each set is
arranged to heat a plurality of separate pipelines.
[0036] In the embodiments according to the present invention, the power transmission cable
can extend for instance at least 30 km between the power supply and said power conditioning
arrangement.
[0037] With the term direct electric heating cable (DEH cable) is meant a cable provided
with alternating electric current in order to heat a subsea pipeline adapted to carry
hydrocarbons. In the art this comprises solutions known as direct electric heating.
Example of embodiment
[0038] While the invention has been described in general terms above, a more detailed example
of embodiment will be given in the following with reference to the drawings, in which
- Fig. 1
- is a principle sketch of a subsea pipeline being heated with a direct electrical heating
assembly which is powered from a floating surface installation;
- Fig. 2
- is a perspective view of a thermally insulated steel pipe having a direct electrical
heating cable and two power transmission cables strapped onto it;
- Fig. 3
- is a schematic drawing showing a setup from the prior art, showing a power supply
arrangement arranged at a surface or onshore location;
- Fig. 4
- is a schematic drawing of the same features as shown in Fig. 3, however with a power
transmission cable arranged between a subsea capacitor arrangement and the remaining
components of the power supply arrangement;
- Fig. 5
- is a schematic view of an end fed DEH assembly according to the present invention;
- Fig. 6
- is a schematic view of a midpoint fed DEH assembly according to the present invention;
- Fig. 7
- is a schematic view of an end fed DEH assembly comprising a plurality of heating cable
sections;
- Fig. 8
- is a schematic view of a midpoint fed DEH assembly comprising a plurality of heating
cable sections;
- Fig. 9
- is a schematic view of a DEH assembly combining end feeding and midpoint feeding;
- Fig. 10
- is schematic view of another DEH assembly combining end feeding and midpoint feeding;
- Fig. 11
- is a schematic view of a possible power conditioning arrangement being employed with
a DEH assembly according to the invention;
- Fig. 12
- is a perspective view of the power conditioning arrangement shown in Fig. 11;
- Fig. 13
- is a principle perspective view of a variable capacitor element in the power conditioning
arrangement shown in Fig. 11;
- Fig. 14
- is a principle perspective view of the variable capacitor element shown in Fig. 13
in an adjusted position;
- Fig. 15
- is a side view of the variable capacitor element shown in Fig. 14;
- Fig. 16
- is a schematic view of an embodiment according to the invention;
- Fig. 17
- is schematic view of a DEH assembly according to a further embodiment of the present
invention, without a capacitor arrangement;
- Fig. 18
- is a schematic view of a DEH assembly according to the invention, wherein different
pipes are heated with DEH cables which are fed from the same power conditioning arrangement;
and
- Fig. 19
- is a schematic view of a DEH assembly according to the invention, wherein a plurality
of sets with parallel extending pipelines are provided with DEH cables fed from a
common power conditioning arrangement.
[0039] Fig. 1 shows a part of a hydrocarbon conducting pipeline 1 arranged on the seabed.
Along a section of the pipeline 1 is a direct electrical heating cable (DEH cable)
3. The DEH cable 3 connects to the said section of the pipeline 1 in two locations
and provides that alternating electric current flows through the steel of the pipeline
1, between the said locations. At the locations of electric contact between the DEH
cable 3 and the steel of the pipeline 1, there is also contact to the ambient sea
water. Thus, some current will flow through the sea water, along the pipeline.
[0040] Between the DEH cable 3 and a power supply arranged on a floating installation 5
extends a power transmission cable 7. It is also known to provide power through a
power transmission cable 7 from an onshore location.
[0041] Fig. 2 is a perspective cutaway view of the pipeline 1. Onto the pipeline 1 there
are strapped one DEH cable 3 and two power transmission cables 7. This technique is
known in the art as
piggyback cabling. It should be noted that the power transmission cables 7 shown strapped onto
the pipeline 1 in Fig. 2 are not necessarily used to feed power to the DEH cable 3.
I.e. they may be used to feed other DEH cables than the one shown, or to feed other
subsea equipment.
[0042] On the steel section of the pipeline 1 there is arranged thermal insulation. This
reduces the heat loss to the ambient sea water when the steel is heated.
[0043] Fig. 3 is a schematic drawing showing a setup from the prior art, namely the patent
application publication
EP2166637. The drawing shows a power supply arrangement adapted to provide electric current
to a DEH cable arranged subsea, such as the DEH cable 3.
[0044] Fig. 4 is a modification of the drawing shown in Fig. 3, according to an embodiment
of the present invention. In this embodiment, the capacitor arrangement which is arranged
before the DEH cable 3, is arranged at a subsea location, close to the DEH cable 3.
As a result of this, a power transmission cable 7 is arranged between the DEH cable
3 and the other parts of the power supply. As illustrated in Fig. 1, the power transmission
cable 7 extends from a surface location (or an onshore location) down to the DEH cable
3.
[0045] Fig. 5 and Fig. 6 show two types of setup for a DEH assembly according to the present
invention. In these embodiments, as well as for additional embodiments to be described
later with reference to additional drawings, it is assumed a carbon steel pipeline
of 76,2 cm (30"), and power transmission cables of 52 kV. It should however be clear
to the person skilled in the art that the invention is not limited to these constraints.
Thus the pipeline diameter may be smaller or larger, and power transmission cables
of higher or lower voltage may be employed, for instance 132 kV. In 2011 the upper
limit for electrical subsea connectors or penetrators recognized by the industry was
132 (145) kV, ref. Mecon DM 145 kV. Furthermore, the embodiments described herein
are not restricted to use at deep waters, such as 1000 to 2000 meters. However the
described embodiments according to the invention are well suited for such depths.
[0046] In the embodiment shown in Fig. 5, approximately 50 km of thermally insulated pipeline
1 is heated with a DEH assembly according to the invention. From a not shown power
supply, which for instance can be arranged on a floating installation or an onshore
facility, electric power is supplied through a power transmission cable 7. The power
transmission cable 7 has three separate conductors or phases (as indicated with the
three tilted lines schematically crossing the power transmission cable 7).
[0047] The three phase power transmission cable 7 connects to a power conditioning arrangement
100. In this embodiment, the power conditioning arrangement 100 comprises a capacitor
arrangement 110 and a transformer 120. To the power conditioning arrangement 100 a
DEH cable 3 is connected, which extends along the pipeline 1. The electric power delivered
by the power transmission cable 7 can be modified and/or compensated at the subsea
location to fit the inductive load of the DEH cable 3 (i.e. the DEH cable and the
connected pipeline). That is, in this embodiment the delivered power from the power
transmission cable 7 is, in the power conditioning arrangement 100, transformed as
a single phase load where the voltage level is decreased (current is increased) and
the power factor (cos ϕ) is adapted to suit an inductive load.
[0048] Still referring to Fig. 5, from the power conditioning arrangement 100 a jumper connects
to a first connection point 9 to the pipeline 1 (left hand side of Fig. 5). At the
opposite end of the pipeline 1 section in question, the DEH cable 3 connects to a
second connection point 9, 50 km away. The connection points 9 are arranged in a current
transfer zone 11 (CTZ), provided with anodes 13. Between the current transfer zones
11, there are also arranged intermediate anodes 15 for cathodic protection of the
pipeline, particularly in case of cracks in the coating / thermal insulation. The
intermediate anodes 15 also function as earth points for the pipe. The embodiment
shown in Fig. 5 is referred to as an end point fed system, in which the two single-phase
terminals are connected to the two opposite ends of a pipe section.
[0049] Fig. 6 schematically illustrates another embodiment of the present invention. In
this embodiment the midpoint fed system is employed. In this embodiment, two phases
are used, one connected to respective ends of a pipeline section of approximately
100 km. The length of the pipeline 1 which is heated with the two phases is thus twice
the length heated in the embodiment shown in Fig. 5 (employing the end point fed system).
Although not shown in Fig. 6, one could also connect the point in between the two
distant connection points 9 to earth (a third conductor to the pipeline midpoint from
capacitors on the transformer).
[0050] As shown in Fig. 6, two DEH cables 3 extend out from the power conditioning arrangement
100. The DEH cables 3 extend in opposite directions along the pipeline 1 which is
to be heated by the DEH assembly. Corresponding to the features of the embodiment
shown in Fig. 5, the DEH cables 3 connect to respective connection points 9 (100 km
apart) arranged within a current transfer zone 11.
[0051] In this embodiment, as shown in Fig. 6, the power conditioning arrangement 100 converts
the three phases in the power transmission cable 7 into two phases, of which one is
applied on each of the respective DEH cables 3.
[0052] In the embodiments shown in Fig. 5 and Fig. 6, the capacitor arrangement 110 will
adapt the electric power delivered to the DEH cable(s) 3, as the DEH cable(s) 3, together
with the pipeline 1 which shall be heated constitute an inductive load. As a result,
less current flows in the power transmission cable 7 and hence a smaller cable with
less conductor (copper) cross section can be installed. The needed conductor cross
section may be reduced to approximately ½ to ¼ of the cross section of the similar
prior art solutions without the subsea capacitor arrangement 110.
[0053] Fig. 7 and Fig. 8 schematically show a DEH layout where the pipeline 1 is divided
into three heated pipeline sections 1a. In both embodiments electric power is delivered
through a 52 kV power transmission cable 7. In the embodiment shown in Fig. 7, a (not
indicated) DEH cable 3 extends between two connection points 9 on each side of each
of the three pipeline sections 1 a. Between each of the three DEH cables 3 and the
power transmission cable 7 there is connected a power conditioning arrangement 100
comprising a capacitor arrangement 110 (cf. Fig. 5). In this embodiment, each pipeline
section 1 a is approximately 50 km long.
[0054] Thus the illustrated DEH assembly heats a pipeline 1 length of approximately 150
km.
[0055] The embodiment shown in Fig. 8 is similar to the one shown in Fig. 7, however a midpoint
fed system is employed, such as the one described with reference to Fig. 6 above.
Also in this embodiment exhibits three pipeline sections 1a, however since the midpoint
fed system is employed each pipeline section 1a can be made longer, such as for instance
50 to 100 km long. Each pipeline section 1 a and associated power conditioning arrangement
100 can correspond to the embodiment shown in Fig. 6.
[0056] Fig. 9 shows another embodiment of a DEH assembly according to the present invention.
In this embodiment, two pipe sections 1 a of 80 km are heated with the midpoint fed
system, whereas a third pipe section 1a of 40 km is heated with the endpoint fed system.
The endpoint fed pipe section 1 a of 40 km is close to a power supply and may be partially
above the sea surface. Hence there is no power conditioning arrangement 100 between
the typically two-core power transmission cable 7 and the DEH cable 3, associated
to this pipeline section 1a. As the pipeline 1 continues a long distance along the
seabed, such as to a subsea hydrocarbon well (not shown) the other two pipeline sections
are heated with the DEH assembly according to the present invention. Between the three
phase power transmission cable 7 and the DEH cables 3 there are arranged, in the subsea
location close to the pipeline 1, a power conditioning arrangement 100. In this embodiment,
the power conditioning arrangement 100 comprises a three-to-two phase transformer
120. It also comprises a capacitor arrangement 110 with a capacitor element 115 arranged
between a section midpoint connection 4 to the pipeline at the mid point between the
connection points 9 of the respective pipeline section 1 a, and the transformer 120.
The transformer 120 provides galvanic segregation between the primary side supplied
via the three-phase power transmission cable 7 and the secondary side that is electrically
connected to pipeline via the DEH cable 3 and the midpoint connection 4.
[0057] As will be explained later, with reference to Fig. 16, the section midpoint connection
4 between the said pipeline section midpoint and the transformer 120, may be connected
to the chassis or the outer tank / shell of the transformer 120.
[0058] Fig. 10 shows a particular embodiment exhibiting three approximately equally long
pipeline sections 1 a of 60 km, and a shorter pipeline section of about 20 km. As
with the embodiment shown in Fig. 9, a separate short typically two-core power transmission
cable 7 extend from an onshore power supply to the short pipeline section 1 a of 20
km. For this pipeline section 1 a there is no power conditioning arrangement 100 arranged
subsea or between the power transmission cable 7 and the DEH cable 3. In association
with each of the subsequent three pipeline sections 1 a there is however arranged
a power conditioning arrangement 100. Furthermore, in this embodiment there is not
arranged any section midpoint connection 4 between the transformer 120 and the pipeline
1. In this embodiment, the transformer 120 is a single phase transformer (i.e. a single
phase transformer 120 for each power conditioning arrangement 100). The transformer
120 provides galvanic segregation between the primary side supplied via the three-phase
power transmission cable 7 and the secondary side that is electrically connected to
pipe-line via the DEH cable 3.
[0059] In the embodiment illustrated in Fig. 10, the DEH assembly associated with the three
longest pipeline sections 1 a is coupled to a unique pair of two phases of the three
phase power transmission cable 7. That is, the three respective transformers 120 associated
with the three long (60 km) pipeline sections 1 a are connected to transmission cable
phase L1 + L3, L2 + L3, and L1 + L2, respectively. Between each transformer 120 and
DEH-cable 3, there is coupled a capacitor arrangement 110. With such coupling layout,
one achieves a balanced load on the phases L1, L2, L3 of the power transmission cable
7 when the length or load of each pipe section 1 a is the same.
[0060] Fig. 11 shows a schematic view of a power conditioning arrangement 100, adapted to
be installed in a subsea environment. The power conditioning arrangement 100 has a
capacitor arrangement 110 arranged within a rigid tank 105. The tank 5 is filled with
a liquid, such as an oil. The capacitor arrangement 110 can also have arranged a transformer
arrangement 120 within the same tank 105. Electrically connected to the capacitor
arrangement 110 and/or the transformer arrangement 120 is a pair of electric cables
103 which connect to a pair of penetrators 130. The electric cables 103 may be connected
to the capacitor arrangement 110 by connection to the penetrators 130 in a subsea
environment. The power conditioning arrangement 100 can thus be added to an existing
electric system subsea and/or may be disconnected for maintenance or replacement.
The electric cables 103 may be connected to the DEH cable(s) 3, or may indeed be the
DEH cable(s) 3 itself.
[0061] In order to make the subsea power conditioning arrangement 100 suitable for installation
in a subsea environment, possibly with large ambient pressures, the liquid within
the tank 105 is pressure balanced. The pressure balancing is provided with a pressure
balancing section 135. The pressure balancing section 135 is functionally connected
to the interior of the tank 5 through a pressure balance liquid line 140.
[0062] The pressure balance liquid line 140 extends between the interior of the tank 105
and a main metal bellows 145 which can be filled with oil. The main bellows 145 is
compressible. Thus when the power conditioning arrangement 100 is lowered into the
sea, the ambient pressure will compress the main bellows 145. This results in approximately
the same pressure within the main bellows 145 and the tank 105 as the ambient water
pressure. In order to provide a slightly larger pressure within the main bellows 145
and the tank 105, a weight 150 is arranged on the main bellows 17 in such way that
it preloads or compresses the bellows 145. Thus the pressure in the tank 105 will
always be slightly higher than the pressure of the ambient water. This prevents leakage
of sea water into the tank 105. In order to render it possible to fill or discharge
liquid into or out of the main bellows 145 (such as with an ROV), a connection line
and valve 147 is arranged in association to the main bellows 145.
[0063] Outside the main bellows 145 there can be arranged an auxiliary bellows 155. The
auxiliary bellows 155 encloses the main bellows 145 together with a bottom plate.
The auxiliary bellows 155, i.e. the volume between the auxiliary bellows 155 and the
main bellows 145 can also be filled with oil or another appropriate barrier liquid.
In this way the main bellows 145 is protected from sea water. Corresponding to the
main bellows 145, the auxiliary bellows 155 is also provided with a connection line
and valve 157. In addition the auxiliary bellows 155 is provided with an indication
pin 159 extending upwards from the top of the auxiliary bellows 155. The indication
pin 159 indicates the vertical position of the top of the auxiliary bellows 155 and
thus tells the operator if liquid amount in the auxiliary bellows 155 needs to be
increased or decreased.
[0064] As will be appreciated by the person skilled in the art, the pressure balance function
is provided also without the auxiliary bellows 155. Also, without the auxiliary bellows
155, the indication pin 159 could be arranged on the main bellows 145.
[0065] Surrounding the main bellows 145 and the auxiliary bellows 155 is a rigid enclosure
160 which protects the bellows 145, 155, such as from impacts from falling objects
or collision with an ROV.
[0066] When employing a power conditioning arrangement 100 in the various embodiments according
to the present invention, one may arrange both a capacitor arrangement 110 and a transformer
arrangement 120 within the same tank 105. One may also arrange them in separate tanks.
However one would then have to connect them together with electric jumpers and additional
wet-mate connectors. According to the present invention, there may also be embodiments
without transformers (cf. Fig. 17).
[0067] Fig. 12 shows a more realistic perspective view of the subsea power conditioning
arrangement 100. In this illustration the pressure balancing section 135 also comprises
some bladder compensators 165. These are not present in the embodiment shown in Fig.
11. The bladder compensators 165 are connected to the auxiliary bladder 155 in stead
of the connection line and valve 157 shown in Fig. 11. Each bladder compensator 165
has a rigid vessel holding a gas volume and a liquid volume, wherein the volumes are
separated with a flexible bladder. The liquid line (not shown) extending between the
bladder compensators 165 and the interior of the auxiliary bellows 155 can have a
valve adapted for filling and/or discharging liquid (e.g. oil) into or out of the
bladder compensators 165 and the auxiliary bellows 155.
[0068] It is now referred to the drawings of Fig. 13, Fig. 14, and Fig. 15. These drawings
show principle sketches of a possible variable capacitor arrangement 110. The capacitor
arrangement 110 comprises a set of first plates 111 and a set of second plates 113.
As is not shown but will be appreciated to the person skilled in the art, the set
of first plates 111 are functionally connected to one of the electric cables 103 whereas
the set of second plates 113 are functionally connected to the other electric cable
103 (cf. Fig. 11). Furthermore, the set of second plates 113 is connected to a pivot
rod 115 which is adapted to be pivoted by means of an electric actuator (not shown)
within the tank 105. When the set of second plates 113 is pivoted with respect to
the stationary set of first plates 111, the capacitance varies.
[0069] Fig. 13 shows a situation wherein the first plates 111 are aligned with the second
plates 113. Fig. 14 shows a situation wherein the second plates 113 have been rotated
about 90 degrees with respect to the aligned position shown in Fig. 13. In this position
the overlapping area of the first and second plates is less than in the aligned position,
thereby reducing the capacitance of the capacitor arrangement 110. With additional
rotation of the set of second plates 113, they can be moved into a position in which
substantially no overlapping exists between the first and second plates 111, 113.
The capacitance of the capacitor arrangement can then be practically zero. Fig. 15
shows the same situation as in Fig. 14, in a side view.
[0070] In a more realistic embodiment, the capacitor arrangement 110 will have more plates
111, 113 and the plates can be arranged closer to each other. Furthermore, in stead
of having one capacitor element as shown in Fig. 13, the capacitor arrangement 110
can comprise a plurality of capacitor elements, that is a plurality of the assemblies
shown in Fig. 13. These can be connected in parallel and some or all of them may be
of the variable type. The gaps between the plates 111, 113 can be filled with the
liquid, preferably oil, present in the tank 105.
[0071] Fig. 16 schematically shows the power conditioning arrangement 100 in association
to a midpoint fed pipeline 1 or pipeline section 1 a. In this embodiment, the power
conditioning arrangement 100 comprises a transformer 120 and capacitor arrangement
110. Two of the phases out from the transformer 120 are connected in parallel with
the capacitor arrangement 110. After the capacitor arrangement 110, the two phases
exit the tank 105 through the penetrators 130. One of the phases is connected to one
end of the pipeline section 1 a and is terminated to the pipeline 1. In this embodiment,
the cable 103 exiting from the penetrator 130 is the same cable as the DEH cable 3
which is piggybacked onto the pipeline 1. The second phase is connected to the other
end of the pipeline section 1b and is terminated to the pipeline 1. The third phase
exiting the transformer 120 is functionally connected to the section midpoint connection
cable 4, which connects to the midpoint of the pipeline section 1b.
[0072] In order to reduce the amount of penetrators and thereby the cost and complexity,
the section midpoint connection 4 cable connected to the pipeline section 1 b is short
circuited at the steel structure of the power conditioning arrangement 100, such as
on the exterior face of the tank 105. This can be done in different ways. For example
by connecting the section midpoint connection 4 cable to a steel sleeve and then welding
this steel sleeve to the steel structure of the tank 105. On the inside of the tank
105, the third phase can then be connected to the transformer 120 with a copper cable
that is short circuited to the inner side of the tank 105. By doing this there is
no need for a cable going through the capacitor assembly and therefore one less penetrator
is needed.
[0073] As will be appreciated by the person skilled in the art, the power conditioning arrangement
100 is connected to a not shown power transmission cable 7, as shown in the above
described embodiments.
[0074] Fig. 17 shows an additional embodiment of a subsea DEH assembly according to the
invention. The embodiment corresponds in many respects to the embodiment described
with reference to Fig. 10. However, in the embodiment shown in Fig. 17 the power conditioning
arrangement 100 does not comprise a transformer, hence the various sections with DEH
do not have galvanic segregation. For the adjacent systems galvanic segregation is
provided by the feeding transformers and optionally the receiving transformer in the
far-end if installed.
[0075] Fig. 18 shows a particular embodiment according to the present invention. On the
seabed there are arranged a plurality of different pipelines 3. Each pipeline is arranged
with a DEH cable 3. In this embodiment, each pipeline is heated with an endpoint fed
system, wherein each respective DEH cable 3 is fed with a common power conditioning
arrangement 100. As with the embodiments above, the power conditioning arrangement
100, which is arranged subsea, receives power through a power transmission cable 7.
[0076] Fig. 19 is an embodiment similar to the embodiment shown with reference to Fig. 18.
However, in the embodiment shown in Fig. 19 each DEH cable 3 is arranged in a configuration
to heat a plurality (three) of pipelines 1. That is, each DEH cable 3 is associated
with three pipeline segments that extend between the same locations. Moreover, with
the embodiment shown in Fig. 19, one power conditioning arrangement 100 provides power
to three sets of three DEH cables 3. As will be understood by the person skilled in
the art, with the setup shown in Fig. 19 it will be beneficial to have the pipelines
1 close to each other in order to reduce the necessary length of the DEH cables 3
and the jumpers connecting each pipeline (or each pipeline segment 1a of different
pipelines 1, respectively).
[0077] The person skilled in the art will appreciate that the present invention is suited
for other embodiments than the ones shown above, such as the pipe-in-pipe technique
which is assumed known to the skilled person.
[0078] The above described embodiments can typically be employed with pipelines having a
diameter in the range of e.g. 50,8 cm (20") to 76,2 cm (30") and with a length of
for instance more than 100 km. As shown by dividing the heated pipeline 1 into sections
1 a, a pipeline which is much longer than 100 km can be heated.
[0079] To illustrate the technical advantages brought about with the present invention,
the following example is given. When using the direct electric heating assembly according
to the present invention, one can for instance eliminate 2-10 DEH risers (cf. power
transmission cable 7 in Fig. 1) extending down from a floating platform (typically
for fields with 2-10 heated flowlines), where each riser typically comprises two conductors
with a copper cross section of 1200-1600 mm
2. All these risers can be replaced with one 3 core riser having three conductors with
200 mm
2 to 800 mm
2.
1. A subsea direct electrical heating assembly adapted to heat a hydrocarbon conducting
steel pipeline (1) arranged subsea, the subsea direct electric heating assembly comprising
a direct electrical heating cable (3) extending along and being connected to the steel
pipeline (1) and a power transmission cable (7) receiving electric power from a power
supply (5), arranged onshore or at surface offshore, and feeding the direct electrical
heating cable (3), characterized in that the subsea direct electrical heating assembly further comprises a power conditioning
arrangement (100) arranged at a subsea location, in a position between the power transmission
cable (7) and the direct electrical heating cable (3), wherein the power transmission
cable (7) extends from the offshore or onshore power supply (5) and down to the power
conditioning arrangement (100).
2. A subsea direct electrical heating assembly according to claim 1, characterized in that the power conditioning arrangement (100) comprises a subsea capacitor arrangement.
3. A subsea direct electrical heating assembly according to claim 1 or 2, characterized in that the power conditioning arrangement (100) comprises a transformer (120).
4. A subsea direct electrical heating assembly according to one of the preceding claims,
characterized in that the direct electrical heating cable (3) is arranged along and attached to the pipeline
(1).
5. A subsea direct electrical heating assembly according to one of the preceding claims,
characterized in that it is adapted to heat a plurality of pipeline sections (1a) which each constitutes
a part of a longer pipeline (1) as the direct electric heating assembly comprises
a plurality of direct electric heating cables (3) arranged along and/or in proximity
to the pipeline sections (1 a) and that for each pipeline section (1 a) a said power
conditioning arrangement (100) is arranged between the power transmission cable (7)
and the section heating cables (3) associated to each pipeline section (1a).
6. A subsea direct electrical heating assembly according to one of the preceding claims,
characterized in that power from said power transmission cable (7) is fed to a direct electrical heating
cable (3) adapted to heat a pipeline extending between a subsea well and a compression
facility, through the subsea power conditioning arrangement (100).
7. A subsea direct electrical heating assembly according to one of the claims 2 to 6,
characterized in that the subsea capacitor arrangement (110) is in the kV and kVAr range or above, comprising
a capacitor element (111, 113) arranged within a tank (105) that prevents sea water
entering the tank (105), wherein the tank (105) is pressure balanced and filled with
a pressure compensation fluid.
8. A subsea direct electrical heating assembly according to claim 3 and claim 7, characterized in that the transformer (120) is arranged within the tank (105).
9. A subsea direct electrical heating assembly according to claim 7 or claim 8, characterized in that the capacitor arrangement (110) is a variable capacitor arrangement (110), the capacitance
of which is adjustable between an upper and lower value by means of an actuator arranged
within the tank (105).
10. A subsea direct electrical heating assembly according to one of the claims 3 to 9,
characterized in that the transformer (120) is an adjustable transformer.
11. A subsea direct electric heating assembly according to one of the preceding claims,
characterized in that the power transmission cable (7) comprises three phases (L1, L2, L3) and that three
section heating cables (3) are each connected between a different pair of phases (L1,
L2, L3).
12. A subsea direct electric heating assembly according to claim 11, characterized in that it comprises three sets of section heating cables (3), wherein each set comprises
two or more section cables (3).
13. A subsea direct electric heating assembly according to claim 8, characterized in that the power conditioning arrangement (100) is connected between the power transmission
cable (7) and a midpoint fed pipeline section (1 a), wherein two transformer terminals
exit the tank (105) through penetrators and are connected to respective ends of said
pipeline section (1 a), and that a third transformer terminal is connected to a section
midpoint connection (4) cable that connects to a midpoint on the pipeline section
(1 a) between said respective ends, wherein the section midpoint connection (4) cable
is short circuited to a steel structure of the power conditioning arrangement (100)
as is also the third transformer terminal.
14. A subsea direct electric heating assembly according to any one of the preceding claims,
characterized in that the power transmission cable (7) extends at least 30 km between the power supply
(5) and said power conditioning arrangement (100).
15. A subsea direct electric heating assembly according to any one of the preceding claims,
characterized in that the power conditioning arrangement (100) is connected to a plurality of DEH cables
(3) which are arranged along different pipelines (1).
16. A subsea direct electric heating assembly according to any one of the preceding claims,
characterized in that the power conditioning arrangement (100) is connected to a plurality of sets of a
plurality of DEH cables (3), wherein each set is arranged to heat a plurality of parallel
pipelines (1).
1. Unterseeische elektrische Direktheizanlage, geeignet um eine unterseeisch angeordnete
hydrokarbonführende Stahlpipeline (1) zu heizen, wobei die unterseeische elektrische
Direktheizanlage ein elektrisches Direktheizkabel (3), welches sich entlang der Stahlpipeline
(1) erstreckt und damit verbunden ist, und ein Stromübertragungskabel (7) umfasst,
welches von einer Onshore oder auf einer Offshore-Oberfläche angeordneten Stromversorgung
(5) elektrischen Strom empfängt und das elektrische Direktheizkabel (3) versorgt,
dadurch gekennzeichnet, dass die unterseeische elektrische Direktheizanlage weiterhin eine Stromaufbereitungsanordnung
(100) umfasst, welche an einem unterseeischen Ort in einer Position zwischen dem Stromübertragungskabel
(7) und dem elektrischen Direktheizkabel (3) angeordnet ist, wobei sich das Stromübertragungskabel
(7) von der Offshore- oder Onshore-Stromversorgung (5) und hinunter zur Stromaufbereitungsanordnung
(100) erstreckt.
2. Unterseeische elektrische Direktheizanlage nach Anspruch 1, dadurch gekennzeichnet, dass die Stromaufbereitungsanordnung (100) eine unterseeische Kondensatoranordnung umfasst.
3. Unterseeische elektrische Direktheizanlage nach Anspruch 1 oder 2, dadurch gekennzeichnet, dass die Stromaufbereitungsanordnung (100) einen Transformator (120) umfasst.
4. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass das elektrische Direktheizkabel (3) entlang der Pipeline (1) angeordnet und daran
angebracht ist.
5. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass sie geeignet ist, eine Vielzahl von Pipelineabschnitten (1 a) zu heizen, welche jeweils
einen Teil einer längeren Pipeline (1) bilden, da die elektrische Direktheizanlage
eine Vielzahl von elektrischen Direktheizkabeln (3) umfasst, welche entlang und/oder
in der Nähe eines Pipelineabschnitts (1 a) angeordnet sind, und dass für jeden Pipelineabschnitt
(1 a) eine Stromaufbereitungsanordnung (100) zwischen dem Stromübertragungskabel (7)
und den mit jedem Pipelineabschnitt (1 a) verbundenen Abschnittsheizkabeln (3) angeordnet
ist.
6. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass Strom vom Stromübertragungskabel (7) zu einem elektrischen Direktheizkabel (3) zugeführt
wird, welcher geeignet ist, um eine Pipeline durch die unterseeische Stromaufbereitungsanordnung
(100) zu heizen, welche zwischen einem unterseeischen Bohrloch und einer Verdichtungseinrichtung
sich erstreckt.
7. Unterseeische elektrische Direktheizanlage nach einem der Ansprüche 2 bis 6, dadurch gekennzeichnet, dass die unterseeische Kondensatoranordnung (110) im kV- und kVAr-Bereich oder oberhalb
liegt, umfassend ein in einem Tank (105) angeordnetes Kondensatorelement (111, 113),
welches das Eindringen von Seewasser in den Tank (105) verhindert, wobei der Tank
(105) druckausgeglichen ist und mit einem druckausgleichenden Fluid gefüllt ist.
8. Unterseeische elektrische Direktheizanlage nach Anspruch 3 und Anspruch 7, dadurch gekennzeichnet, dass der Transformator (120) im Tank (105) angeordnet ist.
9. Unterseeische elektrische Direktheizanlage nach Anspruch 7 oder Anspruch 8, dadurch gekennzeichnet, dass die Kondensatoranordnung (110) eine variable Kondensatoranordnung (110) ist, deren
Kapazität zwischen einer oberen und einem unteren Wert durch einen im Tank (105) angeordneten
Aktuator einstellbar ist.
10. Unterseeische elektrische Direktheizanlage nach einem der Ansprüche 3 bis 9, dadurch gekennzeichnet, dass der Transformator (120) ein einstellbarer Transformator ist.
11. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass das Stromübertragungskabel (7) drei Phasen (L1, L2, L3) umfasst, und dass drei Abschnittsheizkabel
(3) jeweils zwischen verschiedenen Paaren der Phasen (L1, L2, L3) verbunden sind.
12. Unterseeische elektrische Direktheizanlage nach Anspruch 11, dadurch gekennzeichnet, dass sie drei Sätze von Abschnittsheizkabeln (3) umfasst, wobei jeder Satz zwei oder mehr
Abschnittskabel (3) umfasst.
13. Unterseeische elektrische Direktheizanlage nach Anspruch 8, dadurch gekennzeichnet, dass die Stromaufbereitungsanordnung (100) zwischen dem Stromübertragungskabel (7) und
einem Mittelpunktpipelineversorgungsabschnitt (1a) verbunden ist, wobei zwei Transformatorklemmen
aus dem Tank (105) durch Durchstoßkörper austreten und mit den jeweiligen Enden des
Pipelineabschnitts (1a) verbunden sind, und dass eine dritte Transformatorklemme mit
einem Abschnittsmittelpunktverbindungskabel (4) verbunden ist, welches einen Mittelpunkt
auf dem Pipelineabschnitt (1 a) zwischen den jeweiligen Enden verbindet, wobei das
Abschnittsmittelpunktverbindungkabel (4) mit einer Stahlstruktur der Stromaufbereitungsanordnung
(100) kurzgeschlossen ist, so wie auch die dritte Transformatorklemme.
14. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass das Stromübertragungskabel (7) sich zumindest 30 km zwischen der Stromversorgung
(5) und der Stromaufbereitungsanordnung (100) erstreckt.
15. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass die Stromaufbereitungsanordnung (100) zu einer Vielzahl von DEH-Kabeln (3) verbunden
ist, welche entlang verschiedener Pipelines (1) angeordnet sind.
16. Unterseeische elektrische Direktheizanlage nach einem der vorhergehenden Ansprüche,
dadurch gekennzeichnet, dass die Stromaufbereitungsanordnung (100) mit einer Vielzahl von Sätzen einer Vielzahl
von DEH-Kabeln (3) verbunden ist, wobei jeder Satz zum Heizen einer Vielzahl paralleler
Pipelines (1) angeordnet ist.
1. Ensemble de chauffage électrique direct sous-marin apte à chauffer une conduite d'acier
conduisant un hydrocarbure (1) disposée sous la mer, l'ensemble de chauffage électrique
direct sous-marin comprenant un câble de chauffage électrique direct (3) qui s'étend
le long de la conduite d'acier (1) et est connecté à celle-ci, et un câble de transmission
de puissance (7) qui reçoit une puissance électrique en provenance d'une alimentation
électrique (5), située à terre ou à la surface de l'eau et qui alimente le câble de
chauffage électrique direct (3), caractérisé en ce que l'ensemble de chauffage électrique direct sous-marin comprend en outre un agencement
de conditionnement de puissance (100) agencé en un lieu sous-marin, dans une position
entre le câble de transmission de puissance (7) et le câble de chauffage électrique
direct (3), dans lequel le câble de transmission de puissance (7) s'étend à partir
de l'alimentation électrique à terre ou en mer (5) et jusqu'à l'agencement de conditionnement
de puissance (100).
2. Ensemble de chauffage électrique direct sous-marin selon la revendication 1, caractérisé en ce que l'agencement de conditionnement de puissance (100) comprend un agencement de condensateur
sous-marin.
3. Ensemble de chauffage électrique direct sous-marin selon la revendication 1 ou 2,
caractérisé en ce que l'agencement de conditionnement de puissance (100) comprend un transformateur (120).
4. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que le câble de chauffage électrique direct (3) est agencé le long de la conduite (1)
et est attaché à celle-ci.
5. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce qu'il est apte à chauffer une pluralité de sections de conduite (1a) qui constituent
chacune une partie d'une conduite plus longue (1) étant donné que l'ensemble de chauffage
électrique direct comprend une pluralité de câbles de chauffage électrique direct
(3) agencés le long et/ou à proximité des sections de conduite (1a) et en ce que pour chaque section de conduite (1a), un tel agencement de conditionnement de puissance
(100) est agencé entre le câble de transmission de puissance (7) et les câbles de
chauffage de section (3) associés à chaque section de conduite (1a).
6. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que la puissance en provenance dudit câble de transmission de puissance (7) est transmise
à un câble de chauffage électrique direct (3) qui est adapté pour chauffer une conduite
qui s'étend entre un puits sous-marin et une installation de compression à travers
l'agencement de conditionnement de puissance sous-marin (100).
7. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
2 à 6, caractérisé en ce que l'agencement de condensateur sous-marin (110) se situe à l'intérieur de la gamme
des kV et des kVAr, ou au-dessus, comprenant un élément de condensateur (111, 113)
agencé à l'intérieur d'un réservoir (105) qui empêche l'eau de mer d'entrer dans le
réservoir (105), dans lequel le réservoir (105) est équilibré en pression et est rempli
d'un fluide de compensation de pression.
8. Ensemble de chauffage électrique direct sous-marin selon la revendication 3 et la
revendication 7, caractérisé en ce que le transformateur (120) est agencé à l'intérieur du réservoir (105).
9. Ensemble de chauffage électrique direct sous-marin selon la revendication 7 ou la
revendication 8, caractérisé en ce que l'agencement de condensateur (110) est un agencement de condensateur variable (110)
dont la capacitance est réglable entre une valeur supérieure et une valeur inférieure
au moyen d'un actionneur agencé à l'intérieur du réservoir (105).
10. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
3 à 9, caractérisé en ce que le transformateur (120) est un transformateur réglable.
11. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que le câble de transmission de puissance (7) comprend trois phases (L1, L2, L3) et en ce que trois câbles de chauffage de section (3) sont connectés chacun entre une paire de
phases différente (L1, L2, L3).
12. Ensemble de chauffage électrique direct sous-marin selon la revendication 11, caractérisé
en c qu'il comprend trois ensembles de câbles de chauffage de section (3), dans lequel
chaque ensemble comprend deux câbles de section (3) ou plus.
13. Ensemble de chauffage électrique direct sous-marin selon la revendication 8, caractérisé en ce que l'agencement de conditionnement de puissance (100) est connecté entre le câble de
transmission de puissance (7) et une section de conduite alimentée au point médian
(1a), dans lequel deux bornes de transformateur sortent du réservoir (105) à travers
des pénétrateurs et sont connectées à des extrémités respectives de ladite section
de conduite (1a), et en ce qu'une troisième borne de transformateur est connectée à un câble de connexion de point
médian de section (4) qui se connecte à un point médian sur la section de conduite
(1a) entre lesdites extrémités respectives dans lequel le câble de connexion de point
médian de section (4) est court-circuité sur une structure d'acier de l'agencement
de conditionnement de puissance (100) comme l'est également la troisième borne du
transformateur.
14. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que le câble de transmission de puissance (7) s'étend sur au moins 30 km entre l'alimentation
électrique (5) et ledit agencement de conditionnement de puissance (100).
15. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que l'agencement de conditionnement de puissance (100) est connecté à une pluralité de
câbles de chauffage électrique direct (3) qui sont agencés le long de conduites différentes
(1).
16. Ensemble de chauffage électrique direct sous-marin selon l'une quelconque des revendications
précédentes, caractérisé en ce que l'agencement de conditionnement de puissance (100) est connecté à une pluralité d'ensembles
d'une pluralité de câbles de chauffage électrique direct (3) dans lequel chaque ensemble
est agencé de manière à chauffer une pluralité de conduites parallèles (1).